title: Cionin: a disulfotyrosyl hybrid of cholecystokinin and gastrin from the neural ganglion of the protochordate Ciona intestinalis.
abstract: We have purified an acidic octapeptide from the neural ganglion of the protochordate Ciona intestinalis by a three-step procedure including C18 Sep-Pak fractionation, MonoQ ion-exchange chromatography, and C4 reversed-phase high-performance liquid chromatography. The purification was monitored by an immunoassay specific for the alpha-carboxyamidated COOH terminus common to the mammalian brain-gut hormones, cholecystokinin and gastrin. Automated Edman degradation revealed the sequence Asn-Tyr-Tyr-Gly-Trp-Met-Asp-Phe. In accordance with the high acidity of the peptide, amino acid analysis after cleavage with aminopeptidase M showed that both tyrosyl residues are sulfated. Hence, the structure is Asn-Tyr(SO3)-Tyr(SO3)-Gly-Trp-Met-Asp-Phe-NH2, as also confirmed by identity with the synthetic disulfated peptide in different chromatographic systems. The occurrence of two consecutively sulfated tyrosyl residues after a neutral residue challenges present concepts of consensus sites for tyrosyl sulfation. We conclude that the structure of the peptide, named cionin, suits that of a common ancestor for cholecystokinin and gastrin.
authors.affiliation: Department of Clinical Chemistry, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: A H
authors.initials: AH
authors.lastname: Johnsen
authors.forename: J F
authors.initials: JF
authors.lastname: Rehfeld
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002766:Cholecystokinin / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D002938:Ciona intestinalis / Q000032:analysis*; D005755:Gastrins / Q000032:analysis*; D007202:Indicators and Reagents; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000302:isolation & purification*; D012689:Sequence Homology, Nucleic Acid; D014561:Urochordata / Q000032:analysis*
chemical_list: D005755:Gastrins; D007202:Indicators and Reagents; D009479:Neuropeptides; C063059:cionin; D002766:Cholecystokinin